These disorders result from an overactive or misdirected immune response in the skin. Some are limited to the skin; others are skin signs of systemic autoimmune disease; a few are life-threatening drug reactions.

Autoimmune blistering diseases (contrast with SJS/TEN)

SJS/TEN spectrum by body surface area (BSA) detached: SJS under 10%, overlap 10–30%, TEN over 30%.

Common culprit drugs: allopurinol, carbamazepine, lamotrigine, phenytoin, sulfonamides (including TMP-SMX), nevirapine, oxicam NSAIDs. Onset is usually 4–28 days after starting the drug. Genetic risk: HLA-B*15:02 with carbamazepine (common in many Southeast Asian populations) and HLA-B*58:01 with allopurinol.

Skin signs of systemic autoimmune disease

Raynaud phenomenon: cold or stress triggers digital vasospasm → white (pallor) → blue (cyanosis) → red (reactive hyperemia).

• Distribution, morphology, scale, vesicles, itching severity, sleep disruption
• Mucosal involvement and skin that peels with light pressure (SJS/TEN) — emergency
• Airway: lip, tongue, or throat swelling, hoarseness, stridor (angioedema)
• Medication history (new drugs in the last 8 weeks), exposures, allergies
• Joint pain, fatigue, muscle weakness, dysphagia (systemic disease)
• Psychosocial impact: visible lesions affect self-image, work, and relationships

Psoriasis

• Mild: topical corticosteroids, vitamin D analogs (calcipotriene), tar, keratolytics; scalp: steroid solutions, foams, or shampoos
• Moderate–severe: phototherapy (narrowband UVB), methotrexate, cyclosporine, acitretin, apremilast, deucravacitinib, biologics (TNF, IL-17, IL-23 inhibitors)

Atopic dermatitis

• Daily emollients and gentle skin care are the foundation
• Topical corticosteroids for flares; topical calcineurin inhibitors (tacrolimus, pimecrolimus) for face and folds; topical PDE-4 or JAK inhibitors
• Moderate–severe: dupilumab, tralokinumab, lebrikizumab, nemolizumab, oral JAK inhibitors, phototherapy

Contact dermatitis: identify and avoid the trigger; topical steroids; oral steroid taper for extensive allergic reactions.

Urticaria / angioedema

• Second-generation H1 antihistamines (cetirizine, loratadine, fexofenadine) first-line; dose can be increased up to four-fold for chronic urticaria; omalizumab if refractory
• Anaphylaxis or airway swelling: IM epinephrine first
• ACE-inhibitor angioedema: stop the ACE inhibitor; antihistamines and steroids are often ineffective (bradykinin-mediated)

SJS/TEN

• Stop the suspected drug immediately
• Transfer to a burn unit or ICU; supportive care similar to burn care: fluids, wound care, temperature control, nutrition, pain control
• Daily ophthalmology review; mucosal care; immunomodulators (cyclosporine, etanercept, IVIG) are used in some centers

Systemic autoimmune disease: hydroxychloroquine and sun protection (lupus); calcium channel blockers for Raynaud; immunosuppressants per specialist.

Drug safety

Listed in priority order.

1. Airway — angioedema or anaphylaxis: call for help, give IM epinephrine, oxygen, prepare for airway management
2. SJS/TEN — treat like a major burn
   • Stop the drug, notify the provider
   • Fluid and electrolyte replacement, monitor urine output
   • Protect denuded skin: non-adherent dressings, no adhesive tape, handle gently with draw sheets
   • Warm room, strict asepsis, monitor for sepsis
   • Eye care (lubricants, ophthalmology), mouth care, pain control, nutrition
3. Itch control and skin protection
   • Keep nails short; discourage scratching and rubbing
   • Cool compresses, lukewarm baths, fragrance-free emollients applied right after bathing
   • Loose cotton clothing
4. Medication administration and monitoring (see table)
5. Psychosocial support — body image, anxiety, sleep; peer support groups

• Bathe in lukewarm (not hot) water with mild, fragrance-free cleansers; pat dry; moisturize within minutes
• Do not rub or scratch; keep nails short; wear cotton gloves at night if needed
• Identify and avoid triggers: allergens, irritants, heat, stress, certain drugs
• SLE: avoid sun exposure, use broad-spectrum sunscreen and protective clothing; wash rash areas gently with lukewarm water — avoid hot water and frequent scrubbing
• Raynaud: keep the whole body warm, wear gloves, stop smoking, avoid caffeine and vasoconstricting decongestants, manage stress
• Psoriasis: apply scalp products as directed (part hair, apply to lesions); sunlight in small amounts may help but avoid burns
• Antihistamines: sedating types can impair driving; avoid alcohol
• SJS/TEN survivors: never take the culprit drug again; carry an allergy card or medical alert bracelet; relatives may share genetic risk
• Methotrexate: take once a week on the same day; avoid alcohol; use reliable contraception
• Biologics: report fever or infection; avoid live vaccines

• Psoriasis: silvery-scaled plaques, Koebner phenomenon; methotrexate is weekly
• Atopic dermatitis: itch, dry skin — emollients daily
• Contact dermatitis: ask what the skin touched before symptoms; patch testing
• Urticaria: second-generation antihistamines first; sedating antihistamines → no driving
• Angioedema with airway signs → IM epinephrine; ACE inhibitor angioedema → stop the drug
• SJS under 10%, TEN over 30% BSA; Nikolsky positive; stop the drug, manage like a burn
• Culprits: allopurinol, carbamazepine (HLA-B*15:02), lamotrigine, phenytoin, sulfonamides
• SLE: butterfly rash, photosensitivity; lukewarm water, sun protection
• Raynaud: white → blue → red; keep warm, stop smoking
• Scleroderma: thick, tight skin, reduced facial expression
• Dermatomyositis: heliotrope rash, Gottron papules
• Behçet: oral and genital ulcers, uveitis (dry eye points to Sjögren syndrome instead)